Various techniques for electrostatic image transfer are known in the patent literature. U.S. Pat. No. 4,684,238 describes intermediate transfer apparatus in which a plurality of liquid images, which include a liquid carrier having toner particles dispersed therein, are attracted from a photoconductive member to an intermediate belt. Liquid carrier is removed from the intermediate belt by vacuum apparatus and the toner particles are compacted on the intermediate belt in image configuration. Thereafter, the toner particles are transferred from the intermediate belt to the copy sheet in image configuration by electrostatic attraction.
U.S. Pat. No. 4,690,539 shows a system similar to that shown in U.S. Pat. No. 4,684,238 which is suitable for multi-color multiple-pass electrophoretic image transfer.
In U.S. Pat. Nos. 3,318,212 and 3,893,761 there are described methods and devices in which a powder image being transported on a resiliently deformable intermediate support surface is softened and thus rendered sticky while present on that surface and then is transferred and fixed onto a paper receiving support under the influence of pressure.
U.S. Pat. No. 4,015,027 describes an electrophotographic toner transfer and fusing method wherein a heated roller or belt is employed for pressure transfer of dry toner images from an intermediate transfer medium onto paper. At column 11, line 29-column 12 line 38 there appears a detailed discussion of heating of images upon transfer thereof as proposed therein and as taught in the prior art including specifically U.S. Pat. No. 3,591,276 to Byrne.
Reference is made to FIGS. 5a-5c, 6a-6c, 7a and 7b of U.S. Pat. No. 4,015,027. It is seen that in nearly all cases described, the toner is heated to at least its melting point during the transfer stage. In a technique proposed in U.S. Pat. No. 4,015,027 and exemplified by FIG. 6(a), the toner is heated to at least its melting point prior to the transfer zone. In the transfer zone, the toner cools below its melting point during transfer and fusion.
A belt construction characterized in that it has a very low heat capacitance and a thickness of between 15 and about 200 microns is proposed in U.S. Pat. No. 4,015,027. In one embodiment the belt comprises a 50 micron layer of aluminized Kapton having a 25 micron coating of silicon rubber. Another embodiment employs a 12.5 micron layer of stainless steel instead of the Kapton together with a silicon rubber coating. A reflecting layer is incorporated in the belt to reduce heating thereof.
Reference is now made to the following published patent applications and issued patents in the field of electrophotography: GB published Patent Applications Nos. 2,169,416A and 2,176,904A and U.S. Pat. Nos. issued 3,990,696, 4,233,381, 4,253,656, 4,256,820, 4,269,504, 4,278,884, 4,286,039, 4,302,093, 4,326,644, 4,326,792, 4,334,762, 4,350,333, 4,355,883, 4,362,297, 4,364,460, 4,364,657, 4,364,661, 4,368,881, 4,378,422, 4,392,742, 4,396,187, 4,400,079, 4,411,976, 4,412,383, 4,413,048, 4,418,903, 4,420,244, 4,435,068, 4,439,035, 4,454,215, 4,460,667, 4,473,865, 4,480,825, 4,501,486, 4,522,484, 4,531,824, 4,538,899, 4,582,774, 4,585,329, 4,586,810, 4,589,761, 4,598,992, 4,603,766, 4,620,699, 4,627,705, 4,678,317, the disclosures of which are incorporated by reference herein.